The BBC is to move away from traditional 19th century-set "bonnet" dramas in favour of a grittier look at the period and a new focus on other historical eras.

This change, which follows the appointment of Ben Stephenson, 31, as head of drama commissioning, will mean that there will be less of the likes of Tess of the D'Urbervilles, Cranford, Oliver Twist, Jane Eyre, Daniel Deronda and Pride and Prejudice.

In their place the BBC is planning more period dramas along the lines of this week's The Diary of Anne Frank and the remake of John Buchan's spy novel, The 39 Steps, which was shown over Christmas.

The move comes after ratings dipped for BBC1's most recent costume drama, Charles Dickens's Little Dorrit, which sank to a low of 2.5 million viewers for one midweek episode last month. By comparison, The Diary of Anne Frank pulled in around 4.5 million viewers, while The 39 Steps, starring the former Spooks actor Rupert Penry-Jones, attracted 7.3 million.

A BBC drama insider said: "There is to be an evolution in the presentation of period dramas, moving away from classic 19th century so-called 'bonnet' dramas to looking at other periods of history. This will allow us to look at other times and places in British and world history. The aim is to give drama audiences something new and different to enjoy."

The BBC insider said that traditional costume dramas would not be abandoned altogether, with the probability of a further as yet undisclosed adaptation later this year.

However, the BBC will focus on the new type of period drama. An adaptation of the award-winning novel Small Island, about Jamaican immigrants to Britain in the 1940s, and Desperate Romantics, about a group of "vagabond painters and poets" set among the "alleys, galleries and flesh houses of 19th-century industrial London", will be among the first to be broadcast later this year.

The BBC also plans to air fewer of its dramas in half-hour episodes. Even though the format has had some success, notably the award-winning Bleak House in 2005, Little Dorrit struggled in the ratings, with viewers seemingly preferring to watch the hour-long repeat of its two midweek episodes in the more traditional costume drama viewing time of Sunday evening.

The change in thinking at the BBC follows the appointment of Stephenson to replace the long-serving Jane Tranter at the end of last year, when she moved to Los Angeles.

A BBC spokesman said: "Drama on the BBC constantly evolves and we will be looking at different eras of period drama this year."